It is known that the development of colorectal tumor needs several sequential abnormality of chromosome in 5p, I8q and 17p and chromosomal abnormality in 17p especially causes malignant transformation of colorectal tumor. The mutation of p53 gene in chromosome 17p proceed the loss of that. Abnormal nuclear protein known as mutant p53 protein is expressed in the early phase of malignant transformation of colorectal tumor. We examined the mutant p53 protein in 115 paraffin-embedded colorectal tumors and normal tissues(group 1: 15 normal tissues, group 2; 30 adenomas and group 3; 70 adenocarcinoma) by immunohistochemical method using monoclonal antibody to the mutant p53 protein. The degree of positive expression of the mutant p53 protein in each group was graded and it was compared in accordance with several prognostic factors of colorectal cancer. In normal tissues and adenomas, positive expression of the mutant p53 protein was not found. In adenocarcinoma, the mutant p53 protein was positively expressed with gradual decreasing tendency from 50.0% of Dukes' A, 48.0% of Dukes' B, 40.9% of Dukes' C to 26.7 % of Dukes' D. The positivity of Dukes' A, B, and C was significantly different from that of Dukes' D.(p<0.05). The mutant p53 protein in adenocarcinoma without lymph nodes involvement, lymphatic invasion, perineural invasion and vein invasion was positively expressed as 48.5%, 47.8%, 50.0% and 44.1%, respectively. That was expressed higher than 39.4% , 38.3%, 20.0% and 27.3% in same group with positive pathologic findings(p<0.05, *p<0.01). The mutant p53 protein in adenocarcinomas of rectum and ascending colon was positively expressed by 48.7% and 40.0%. That was expressed higher than 33.3% and 22.2% in same group of sigmoid colon and transverse and descending colon. The mutant p53 protein was positiveiy expressed in well and morderately differentiated adenocarcinoma as 45.5% and 45.3%. None of poorly differentiated adenocarcinomas and mucinous carcinomas positively expressed, From the above experiment, we found that the mutant p53 protein was exclusively expressed in adenocarcinoma and that positive expression rate was reversely correlated to the clinical staging and severity of invasiveness. In conclusion, we thought that the expression of the mutant p53 protein might have a prognostic value in the colorectal cancer.
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